Performance Of Electrolyte Research Articles

Experimental study of performance enhancement in PEMEC with titanium mesh flow structure via in-situ temperature measurement

A proton exchange membrane electrolysis cell (PEMEC) is a promising method for hydrogen production. However, the flow-field structure of PEMEC presently has the disadvantages of poor fluidity and uneven heat distribution. A titanium mesh flow field was, therefore, proposed to replace the traditional parallel channel structure. A single-cell test platform was set up in this study, and a new in situ temperature measurement method was proposed. The temperature variation and electrolysis performance of titanium mesh structures were studied experimentally. The results demonstrated that the polarization performance of the titanium mesh structure was enhanced compared to that of the parallel structure. In situ measurements showed that the temperature increased and the voltage decreased with an increase in the inlet temperature and flow rate, with the rate of change gradually decreasing. The temperature distribution in the titanium mesh structure was more uniform than that in the parallel structure. When the current density and inlet flow rate step were changed, the voltage stabilized within 12 s. After 100 h of operation, the voltage of the parallel structure and titanium mesh structure increased by 0.12 V and 0.07 V, respectively, indicating good dynamic and duration performance.

Synergistic effect of FeOOH cocatalyst and Al2O3 passivation layer on BiVO4 photoanode for enhanced photoelectrochemical water oxidation

BiVO4 is one of the most attractive photoanodes for water oxidation due to its 2.4 eV narrow band gap, suitable band edge position, good stability in aqueous solution, low cost and non-toxicity. However, due to some inherent disadvantages such as low carrier mobility, severe charge recombination and slow water oxidation kinetics, the actual BiVO4 photocurrent density is often lower than the theoretical value of 7.5 mA cm−2. In this paper, BiVO4 was modified by alkali-treated Al2O3 passivation layer and FeOOH, and the photocurrent density of BiVO4 reached an astonishing 3.8 mA cm−2 at 1.23 VRHE, and the ABPE (applied bias photon-to-current efficiency) was close to 1 %. The detailed structural characterization and electrochemical test show that Al2O3 prepared by ALD (atomic layer deposition) can play a role in passivation of BiVO4 surface state after alkali treatment, inhibit electron hole recombination on BiVO4 surface, and accelerate hole transfer. As a hole storage layer and catalyst layer, FeOOH promoted the interfacial hole transfer, increased the active sites at the electrode electrolyte interface, and significantly increased the water oxidation activity. This work provides a novel method to enhance the performance of water electrolysis by using ALD to assist passivation of bismuth vanadate photoanode surface states.

Utilizing electrooxidation for textile effluent wastewater treatment and simultaneous electrocatalytic hydrogen production: Transforming waste into energy and promoting water reuse in a circular economy context

Textile effluent wastewater poses a serious environmental risk because of its high concentration of pollutants, which include organic compounds, heavy metals, and dyes. The present study investigates the technical and economic feasibility of hybrid water electrolysis performances. Specifically, real textile effluent wastewater was utilised to examine simultaneous abatement and electrochemical hydrogen production. The treated water can be recycled in the textile mill, offering the benefits of trash-to-treasure and cost savings through the circular economy. In addition to reducing the environmental impact of textile wastewater, the synergistic approach seeks to maximise its potential for producing hydrogen as clean energy. Here, the commercially available stainless sheet was used as the anode in the electrochemical setup system and the two-dimensional Ti3C2TX MXene was used as the catalyst embedded cathode. The optimal electrode-electrolyte parameter settings resulted in an 83 % decrease in COD level and a degradation efficiency of about 88 %. The potential for widespread adoption in the textile industry is highlighted by the discussion of the economic viability and environmental advantages of using wastewater from textile effluents for pollutant degradation and hydrogen production. Hence, the energy estimation was looked at and estimated in order to evaluate the process viability. For instance, the hybrid electrolysis process uses a very small amount of electricity (0.825 kWh m−3 order−1) and has an apparent operating current (30 mA/cm2). This work could serve as a guide for the methodical assessment and choice of hybrid water electrolysis using actual wastewater. The electrode's recyclability and reuse were proven for possible commercial applications. The stability of the Ti3C2TX electrode over a wide pH range was investigated in order to produce hydrogen on a big scale at a reasonable cost.

Accurately prepared the large-area and efficiently 3D electrodes for overall seawater splitting

How to achieve accurately regulation of catalytic electrodes is the challenge of designing high-performance catalytic electrodes. In this work, large area, high stability and excellent conductivity electrode are prepared via one-step mild (298 K) electroplating method and precise control of electroplating parameters on nickel foam (FeNi@NF). The FeNi@NF electrode catalyst the hydrogen/oxygen evolution reaction (HER/OER) in simulate seawater (1.0 M KOH + 0.5 M NaCl), and achieves the current density of 100 mA cm−2 with only 287 mV and 323 mV overpotential. The alkaline electrolyzer drives 100 mA cm−2 for overall water splitting at a low voltage of 1.73 V. More importantly, the catalytic performance durable for more than 5 days at the industrial current density (1000 mA cm−2), and the designed large-area 25.0 cm2 catalytic electrode can achieve stable operation of industrial proton exchange membrane electrolyser. This preparation strategy provides a new idea for the current research of energy engineering and energy storage.

Enhanced Oxygen Evolution Reaction Performance of NiMoO4/Carbon Paper Electrocatalysts in Anion Exchange Membrane Water Electrolysis by Atmospheric-Pressure Plasma Jet Treatment.

NiMoO4 was grown on carbon paper (CP) by a hydrothermal method. A rapid and high-temperature atmospheric-pressure plasma jet (APPJ) process was used to generate more oxygen-deficient NiMoO4 on the CP surface to serve as an electrode material for the oxygen evolution reaction (OER). After 60 s of APPJ treatment, the overpotential of the electrode at 100 mA/cm2 decreased to 790 mV and that at 10 mA/cm2 decreased to 368 mV. Additionally, the charge transfer resistance decreased from 2.8 to 1.2 Ω, indicating that APPJ treatment effectively reduced the electrode overpotential and impedance. The effect of NiMoO4/CP/APPJ-60 s on the anion exchange membrane water electrolysis (AEMWE) system was also tested. At a system temperature of 70 °C and current density of 100 mA/cm2, the energy efficiency reached 95.1%, and the specific energy consumption decreased from 4.02 to 3.83 kWh/m3. These results demonstrate that the APPJ-treated NiMoO4/CP electrode can effectively enhance the OER performance in water electrolysis and improve the energy efficiency of the AEMWE system. This approach shows promise in replacing precious metal electrodes, thereby potentially reducing the cost and providing an environmentally friendly alternative.

Study on the influence characteristics of multi-working condition parameters on membrane electrode type CO2 electrolyzer

The electrochemical conversion of carbon dioxide (CO2) into basic chemicals or carbon-based fuels is a promising new strategy for carbon resource utilization. Within this domain, solid-electrolyte CO2 electrolyzer demonstrate significant potential for the continuous production of pure formic acid solutions. This study, leveraging a 4 cm2 visualization electrolyzer, explores the impact of three working condition parameters on performance: working voltage, gas flow rate, and the intermediate chamber water flow rate. It compares the variations in current density, formic acid concentration, and the distribution of liquid water on the cathode side under different working conditions. The results indicate that the working voltage, current density, and formic acid yield are all positively correlated; overly low gas flow rates can lead to CO2 deficiency and diminished electrolyzer performance; concentration control of the formic acid solution is effectively achieved by adjusting the intermediate chamber water flow rate; and during the electrolyzer reaction process, almost all of the liquid water is positioned at the bends downstream of the cathode flow channel.

Interface Engineering of Flower-like Co 2 P/WO 3-x /Carbon Cloth Catalysts with Oxygen Vacancies for Efficient Oxygen Evolution Reaction.

The Constructing an efficient and low-cost oxygen evolution reaction (OER) electrocatalyst is critical for improving the performance of electrolysis in alkaline water. In this study, a self-supported electrocatalyst of flower-like cobalt phosphide and tungsten oxide (Co2P/WO3-x/CC) was prepared on carbon cloth (CC)surface by hydrothermal reaction with solution immersion etching and phosphorization annealing under H2/Ar atmosphere. This strategy can generate oxygen vacancies (OV), improving the speed of charge transfer between cobalt phosphide (Co2P) and tungsten oxide (WO3-x) components. The catalyst greatly increases the electrochemical active surface area, which is beneficial for efficient oxygen evolution. Electrochemical testing studies show that in 1.0 M KOH solution, Co2P-WO3-x/CC catalyst exhibits good OER activity, with a low overpotential of 254 mV at 10 mA cm-2, a small Tafel slope of 58.32 mV dec-1. The synergistic effect of oxygen vacancies and Co2P with WO3-xcan regulate electronic structures, expose more active sites, and cooperatively enhancing the OER activity. This study provides a workable strategy for preparing efficient non-noble metal OER electrocatalysts on engineered interfaces and OV.

Rational Design of Ultrahigh-Loading Ir Single Atoms on Reconstructed Mn─NiOOH for Enhanced Catalytic Performance in Urea-Water Electrolysis.

Investigating advanced electrocatalysts is crucial for improving the efficacy of water splitting to generate environmentally friendly fuel. The discovery of highly effective electrocatalysts, capable of driving oxygen evolution reaction (OER) and urea oxidation reaction (UOR) in urea-alkaline environments, is pivotal for advancing large-scale hydrogen production. This study aims to introduce a new method that involves creating nanosheets of high-loading iridium single atoms embedded in a manganese-containing nickel oxyhydroxide matrix (Ir@Mn─NiOOH). These nanostructures are derived from self-supported hydrate pre-catalyst nanosheets grown on nickel foam and then activated through electrochemical etching pretreatment. The Ir@Mn─NiOOH nanoarchitecture displays outstanding electrocatalytic activity, having a low overpotential of just 258mV and a potential of 1.319V (at 10mAcm-2) for OER and UOR, respectively. Such extraordinary catalytic characteristics of Ir@Mn─NiOOH is mainly owing to the strong synthetic electronic interaction between Ir single atoms and Mn─NiOOH, which can change its electronic characteristics and boost electrochemical catalytic sites. This research presents a new way to produce exceptionally efficient catalysts by adding a synergistic effect to complex multi-electron processes.

Correlation Between Microscopic Current Fluctuations Observed at Ultra-Microelectrodes and Macroscopic Bulk Electrolysis Performance in Redox-Active Microemulsions

Abstract Microemulsions (µEs) have been proposed as redox flow battery (RFB) electrolytes that maximize ionic conductivity and charge capacity by synergizing two immiscible phases. However, charge transfer during electrolysis in µEs is poorly understood. Here, we show that ultramicroelectrode electrolysis of ferrocene-loaded µEs - 20%, 60%, and 90% water - reveals stochastic current fluctuations. These are differentiated in the scanning electrochemical microscopy (SECM) geometry, where power spectral density analysis showed distinct changes in the frequency contributions. SECM in the substrate generation-tip collection mode showed that fluctuations arise under mass-transfer control. Significant differences in the diffusion coefficient of ferrocene species were deducted from SECM approach curves, suggesting phase transfer behavior. Using bulk electrolysis, we calculated the charge accessibility and cycling behavior in the µEs. A decrease in the stochastic behavior of the µEs seems to correlate to a higher accessibility and cycling performance, with the 90% water µE displaying the best reversibility and the 60% the lowest. Altogether, these results suggest that Marangoni-type convection driven by concentration gradients and/or µE restructuring during charge transfer play a role in the electrochemical performance of µEs. This presents opportunities for screening and diagnosing the performance of these emerging RFB electrolytes.

Experimental investigation on the electrical and hydrogen-production performance of a novel PEM electrolyzer driven by CdTe PV with a tracking system

Addressing the challenges of intermittent and variable energy supply, solar hydrogen production via electrolysis has garnered significant attention due to its unique advantages, emerging as a hot topic in the scientific research domain. However, the application of this technology is currently mainly related to the non-tracking system, which undergoes a rapid change in solar irradiation during the day. To expand the matching relationship of solar irradiation, PV characteristics, and electrolyzer, this paper proposes the development of a Proton Exchange Membrane (PEM) electrolyzer driven by Cadmium Telluride (CdTe) photovoltaic (PV) modules with a tracking system for hydrogen production. An experimental platform was set up in Chengdu and the performance tests were carried out for different operating modes during summer. The experimental results demonstrate that the average electrical and hydrogen production efficiencies of the system are 13.11% and 7.88%, respectively, on a sunny day, with a total of 566.7 L of hydrogen produced within 7 h of operation. Furthermore, the solar irradiation received by the tracking surface of the system is significantly enhanced by 10.29% in comparison to the horizontal surface. On a cloudy day with an electrolyzer inlet water temperature of 45 °C, the system has the potential to achieve a hydrogen production efficiency of 11.15 %. At a constant current density of 1.0 A/cm2, the efficiency of the electrolysis process increased by 2.07% and 1.25% for each 10 °C increase in the temperature of the electrolyzer, having an inlet temperature of 35 °C. This study offers a novel approach for a PV-PEM system with a higher hydrogen production efficiency while also establishing a robust foundation for technology optimization and broader implementation.

Nanoflower-like NiCoFe layered hydroxide by in-situ electrochemical corrosion as highly efficient electrocatalyst for water oxidation

Layered double hydroxides have been widely applied for oxygen evolution reaction (OER) in the alkaline water electrolysis. However, the issues of poor connection between the catalyst and nickel foam and the specific mechanisms for active sites has not been fully documented. In this study, the in-situ nickel foam etching in a mixed solution of ferric chloride and cobalt nitrate at low temperatures was adopted for NiCoFe layered ternary hydroxides (NiCoFe LTHs) synthesis with a better tight integration. Physicochemical characterization indicated that the NiCoFe LTHs could grow directly through corroding nickel foam with a nano-flower-like morphology and structures. That is favorable for electron transfer from the catalytic layer to the conductive substrate. With the transition metal ions interaction and the tight integration construction, NiCo1Fe4-LTH-T60/NF presented an enhanced electrolysis performance with the overpotential of 234 mV (1.464 V vs. RHE) at current density of 100 mA cm−2 in 1 M KOH electrolyte. The Tafel slope for NiCo1Fe4-LTH-T60/NF electrode was 36.19 mV dec−1 for an enhanced OER kinetics. Besides, it demonstrated faster interfacial charge transfer process, better intrinsic electrochemical activity and stability in large current stability testing. It was revealed that the synergistic effect of the transition metal ions interaction enhancement and the mechanism of oxygen evolution elementary reaction for NiCo1Fe4-LTH-T60/NF during the water electrolysis by the electrochemical and theoretical calculation. This work provides theoretical basis and experimental support for the design and synthesis of future OER catalyst and substrate, which is significant for hydrogen and oxygen generation from water electrolysis.

Facet Engineering of Cobalt Manganese Oxide for Highly Stable Acidic Oxygen Evolution Reaction

AbstractDeveloping cost‐effective, robust, and durable catalysts for water oxidation in acidic conditions remains a significant challenge for the practical application of proton exchange membrane electrolyzers. Cobalt‐based spinel catalysts, known for their effective oxygen evolution reaction (OER) activity in acidic environments, are promising alternatives to the costly iridium‐based catalysts. However, their application is often limited by poor stability under corrosive acidic conditions and oxidative potential. Here it is demonstrated that doping Co2MnO4 with Ni effectively regulates the structural and electronic properties of the catalysts, enabling stable operation for over 285 h at 100 mA cm−2 in 0.5 m H2SO4. This stability enhancement is primarily due to the increased exposure of the (400) facet, a result supported by theoretical studies. The proton exchange membrane water electrolysis (PEMWE) performance of Ni(5%)Co2MnO4 further demonstrates its potential, achieving 1 A cm−2 at a cell voltage of 2.3 V, with minimal degradation over 100 h at 500 mA cm−2. This study not only provides insights into the design of advanced OER catalysts through the doping of heteroatoms but also offers a pathway to enhance the sustainability and economic viability of acidic OER applications.

In situ regulating the interfacial work function of Ag doped Ni(OH)2 via trace of Fe2+ for efficient water splitting

Traditional approaches for tuning the water electrolysis performance of catalysts through manipulating their work function (WF) have primarily focused on the design of pre-catalysts prior to electrochemical test. Herein, an in situ interfacial WF modulation concept has been developed to synthesize the Fe modified nickel-based hydroxide electrocatalyst with enhanced OER (named as 0.168-FeO-Ag-Ni(OH)2/NF) and HER (0.168-FeH-Ag-Ni(OH)2/NF) activity. The modulator is trace amounts of Fe2+ in 1 M KOH, while the support comprises silver-modified nickel hydroxide, in which the Ag possesses a valence catalysis effect on Ni or Fe sites. Under optimized Fe2+ content, the deposition of Fe facilitates the release of the WF of Ag-Ni(OH)2/NF and accelerates the electron transfer between the catalyst and reaction intermediates. Meanwhile, the charge transfer from Fe to Ni sites coupled with the blue shift of d-band promote the adsorption of water molecules and the desorption of hydrogen protons, thereby accelerating the hydrogen evolution reaction kinetics. Consequently, the OER and HER activity of 0.168-FeO-Ag-Ni(OH)2/NF and 0.168-FeH-Ag-Ni(OH)2/NF enhanced 4.31 and 2.48 times, respectively. Notably, compared with Ag-Ni(OH)2/NF(+)//Ag-Ni(OH)2/NF(−), at a high current density of 1000 mA cm−2, the potential for energy consumption reduction of 0.168-FeO-Ag-Ni(OH)2/NF(+)//0.168-FeH-Ag-Ni(OH)2/NF(−) couple is at least 6 %, which endows it a promising application prospect in the actual electrolytic water system in the future.

Direct Electrolysis of Municipal Reclaimed Water for Efficient Hydrogen Production Using a Bifunctional Non-Noble-Metal Catalyst.

Water electrolysis for green H2 production traditionally requires a stable supply of renewable electricity and pure water. However, spatial separation of renewables and water resources as well as water scarcity per capita in China necessitate unconventional water resources for electrolysis. Reclaimed water produced from municipal wastewater treatment plants is widely distributed with quality improved significantly in recent years, which may be a promising alternative to feedstock. However, there are few reports on the direct use of this wastewater for H2 production. Here, we present a direct electrolysis of reclaimed water for decentralized H2 production by developing a highly efficient and stable bifunctional 3D-dandelion-like (DL) vanadium(V)-doped CoP catalyst grown in situ on Ni foam (NF) in an alkaline electrolyzer. The V-CoP-DL/NF electrode decreases 6.5 and 25% overpotentials of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively, compared to noble-metal Pt (HER) and IrO2 (OER) catalysts, and exhibits exceptional durability, as a voltage required for overall reclaimed water splitting only increases by 80 mV (1.81-1.89 V) after 90 days of operation at a current density of 10 mA cm-2. The maximum stable current can reach 1000 mA cm-2. The impacts of potential pollutants in reclaimed water on the performance of electrolysis and the behavior of major wastewater ions in alkaline electrolyte were investigated. The observed exceptional performance is attributed to the catalyst's unique nanostructure, which enhances charge transfer and reactant/electrolyte diffusion. The in situ growth strategy further enhances the conductivity and stability of the catalyst. This work underscores the feasibility of utilizing reclaimed water instead of pure water as the feedstock for sustainable hydrogen production.

Superhydrophilicity and superaerophobicity Ni/Ni3S4/1T-MoS2 for hydrazine-assisted seawater splitting

The overall hydrazine splitting (OHzS) is a promising strategy to achieve the efficient hydrogen production in seawater through replacing the slow kinetic oxygen evolution reaction (OER) and toxic chlorine evolution reaction (ClOR) by hydrazine oxidation (HzOR). We report an efficient bifunctional electrocatalyst of Ni/Ni3S4/1T-MoS2 on carbon cloth (Ni/Ni3S4/1T-MoS2/CC), which was formed from large layer spacing MoS2 and Ni3S4 with metal-Ni, and was applied as for both hydrogen evolution reaction (HER) and HzOR. The MoS2 had expanded interlayer spacing and showed 1T phase, with significantly improved conductivity and hydrophilicity, which promotes transfer process of reactants. Furthermore, the introduction of Ni/Ni3S4 on the 1T-MoS2 base surface leaded to superhydrophilic and superaerophobic properties, which makes it more conducive to the adsorption of H. The improvement of electrical conductivity induced the excellent HER and HzOR electrocatalytic properties of Ni/Ni3S4/1T-MoS2/CC, which showed an ultralow overpotential of 24 mV and working potential of 0 mV at a current density of 10 mA cm−2, respectively. Inspiringly, Ni/Ni3S4/1T-MoS2/CC also showed excellent performance in hydrazine-assisted alkaline seawater electrolysis, as well as solar panel powered electrolysis of seawater OHzS, therefore, exhibiting great potential for practical applications.

Bis-cationic crosslinked anion exchange membranes based on carbazole-containing polyaromatics with excellent ionic conductivity for alkaline water electrolysis

As the core component in anion exchange membrane water electrolyser (AEMWE), anion exchange membrane (AEM) directly determines the electrolysis performance and long-term durability of AEMWE. Herein, we synthesized novel poly(carbazole-p-terphenylpiperidine) (PCTP-x) copolymers and then prepared a series of bis-cationic cross-linked AEMs (QPCTP-x-bpip) using the Menshutkin reaction between the cross-linker 4,4′-trimethylenebis(1-methylpiperidine) and the alkyl bromide on the polymer side chains. For comparison, non-crosslinked AEMs containing alkylpiperidinium side chains (QPCTP-x-pip) were prepared via a grafting reaction of alkyl bromide with 1-methylpiperidine. The bis-cationic crosslinked membrane exhibited high hydroxide conductivity of 190.0 mS cm−1, and demonstrated outstanding alkaline stability in a 1 M KOH solution at 80 °C, retaining more than 90 % of the initial hydroxide conductivity and tensile strength after 2200 h alkaline treatment. Meanwhile, the flexural carbazole backbone enhanced polymer solubility, enabling the utilization of QPCTP-20-pip as an anion exchange ionomer (AEI) in AEMWE. For the water electrolysis testing, AEMWE employing QPCTP-20-bpip as the AEM and QPCTP-20-pip as the AEI exhibited excellent performance, achieving a current density of 2910 mA cm−2 at 2.0 V using a 1 M KOH feed at 80℃. Moreover, the voltage increase during the in-situ durability test over 200 h was a mere 0.65 mV/h, demonstrating its promising potential for AEMWE applications.

Optimizing NiFe-Modified Graphite for Enhanced Catalytic Performance in Alkaline Water Electrolysis: Influence of Substrate Geometry and Catalyst Loading.

The oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are critical processes in water splitting, yet achieving efficient performance with minimal overpotential remains a significant challenge. Although NiFe-based catalysts are widely studied, their performance can be further enhanced by optimizing the interaction between the catalyst and the substrate. Here, we present a detailed investigation of NiFe-modified graphite electrodes, comparing the effects of compressed and expanded graphite substrates on catalytic performance. Our study reveals that substrate geometry plays a pivotal role in catalyst distribution and activity, with expanded graphite facilitating more effective electron transfer and active site utilization. Additionally, we observe that increasing the NiFe loading leads to only modest gains in performance, due to catalyst agglomeration at higher loadings. The optimized NiFe-graphite composites exhibit superior stability and catalytic activity, achieving lower overpotentials and higher current densities, making them promising candidates for sustainable hydrogen production via alkaline electrolysis.

Numerical study of proton exchange membrane water electrolyzer performance based on catalyst layer agglomerate model

In this work, a two-dimensional two-phase model of proton exchange membrane water electrolyzer (PEMWE) is developed, in which the catalyst layer (CL) is represented using agglomerate model. The effects of CL composition, porous transport layer (PTL) material properties and operating conditions on PEMWE performance are investigated. The results indicate that small size of catalyst agglomerate around 0.25 μm would benefit PEMWE performance. Appropriate increase of catalyst loading, porosity and ionomer volume fraction in the CL improves PEMWE performance, but their further increment leads to high mass transfer resistance, limiting the improvement of electrolyzer performance. The porosity and ionomer volume fraction of the catalyst layer are suggested to be lower than 0.5 and 0.6, respectively. The catalyst loading should be lower than 1.5 mg cm−2 when the CL porosity is higher than 0.3. The PTLs with high permeability, porosity and low contact angle is beneficial for the gas–liquid two-phase flow and avoiding the overheat and water shortage in the electrolyzer. Increasing the inlet velocity accelerates the bubble removal process, but might results in significant temperature drop, degrading the PEMWE performance. The most suitable temperature of inlet liquid is around 353.15 K. The results provide important guidance for the optimization design of high-performance PEMWE.

Reversible Long-Term Operation of a MK35x Electrolyte-Supported Solid Oxide Cell-Based Stack

High-temperature reversible solid oxide cells (rSOC) combine electrolyzer and fuel cell in one process unit which promises economic advantages with unrivaled high electrical efficiencies. However, large temperature gradients during dynamic rSOC operation can increase the risk of mechanical failure. Here, the degradation behavior of a 10-cell stack of the type “MK35x” with chromium-iron-yttrium (CFY) interconnects and electrolyte-supported cells (ESC) developed at Fraunhofer IKTS was investigated in rSOC operation at DLR. Its degradation was evaluated during nominal rSOC operation for more than 3400 h with 137 switching cycles between solid oxide fuel cell and solid oxide electrolysis cell operation of 24 h reflecting intermittent availability of solar energy. The voltage degradation rates of +0.58%/kh and −1.23%/kh in electrolysis and fuel cell operation, respectively, are among the lowest reported in literature. Comparison to a previously published long-term test in steam electrolysis did not show any indication for an increased degradation. Electrochemical impedance spectroscopy measurements were performed for all repeat units to evaluate the degradation behavior in detail. An overall polarization resistance decrease due to an improvement of the oxygen electrode was observed during electrolysis operation but was absent during fuel cell operation.

Heterointerface of nickel-ferric hydroxide / cobalt-phosphide-boride boosting hydrazine-assisted water electrolysis

Sustainable H2 production based on hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HzOR) has attracted wide attention due to minimal energy consumption compared to overall water electrolysis. The present study focuses on the design and construction of heterostructured CoPB@NiFe–OH applied as efficient bifunctional catalysts to sustainable produce hydrogen and remove hydrazine in alkaline media. Impressively, CoPB@NiFe–OH heterointerface exhibits an HzOR potential of −135 mV at the current density of 10 mA cm−2 when the P to B atom ratio was 0.2, simultaneously an HER potential of −32 mV toward HER when the atom ratio of P and B was 0.5. Thus, hydrogen production without an outer voltage accompanied by a small current density output of 25 mA cm−2 is achieved, surpassing most reported catalysts. In addition, DFT calculations demonstrate the Co sites in CoPB upgrades H∗ adsorption, while the Ni sites in NiFe–OH optimizes the adsorption energy of N2H4∗ due to electron transfer from CoPB to NiFe–OH at the heterointerface, ultimately leading to exceptional wonderful performance in hydrazine-assistant water electrolysis via HER coupled with HzOR.